题目内容：

May I speak to Mr.Smith?,（） please.I'll see if she is in.
A Look out B Hold on C Keep up D come on

优质解答

选择B
hold on：稍等
look out：小心
keep up：保持
come on：加油

追问：

Zhang Lin also put up some signs(ask)(for)old computer括号内的适当形式？为什么是asking？